This invention relates to endovascular graft systems for the repair of aneurysms. In particular, this invention relates to an endovascular graft system for use in repairing abdominal aortic aneurysms.
Aortic aneurysms represent a significant medical problem for the general population. Aneurysms within the aorta presently affect between two and seven percent of the general population and the rate of incidence appears to be increasing. This form of vascular disease is characterized by a degradation in the arterial wall in which the wall weakens and balloons outward by thinning. If untreated, the aneurysm can rupture resulting in death within a short time.
The traditional treatment for patients with an abdominal aortic aneurysm is surgical repair. This is an extensive operation involving transperitoneal or retroperitoneal dissection of the aorta and replacement of the aneurysm with an artificial artery known as a prosthetic graft. This procedure requires exposure of the aorta through an abdominal incision extending from the lower border from the breast bone down to the pubic bone. The aorta is clamped both above and below the aneurysm so that the aneurysm can be opened and the prosthetic graft of approximately the same size as the aorta is sutured in place. Blood flow is then re-established through the prosthetic graft. The operation requires a general anesthesia with a breathing tube, extensive intensive care unit monitoring in the immediate post-operative period along with blood transfusions and stomach and bladder tubes. All of this imposes stress on the cardiovascular system. This is a high-risk surgical procedure with well-recognized morbidity and mortality.
More recently, significantly less invasive clinical approaches to aneurysm repair known as endovascular grafting have been proposed. (See, Parodi, J. C., et al. xe2x80x9cTransfemoral Intraluminal Graft Implantation for Abdominal Aortic Aneurysms,xe2x80x9d 5 Annals of Vascular Surgery, 491 (1991)). Endovascular grafting involves the transluminal placement of a prosthetic arterial graft in the endoluminal position (within the lumen of the artery). By this method, the graft is attached to the internal surface of an arterial wall by means of attachment devices such as expandable stents, one above the aneurysm and a second below the aneurysm.
Although endovascular grafting represents a desirable improvement over traditional surgical repair, current endovascular graft systems suffer from certain deficiencies. For example, current endovascular graft systems typically are unsuitable for use in an aneurysm which is torturous. Aneurysms in the aorta create tortuosity as they grow. Aneurysms grow both in diameter and length, thus xe2x80x9cpushingxe2x80x9d the adjacent upper and lower portions of the arteries upward and downward, respectively. Since the aorta is relatively xe2x80x9cfixedxe2x80x9d at the renal arteries, the portion of the aorta below and near the renal arteries becomes bent and curved in order to accommodate the added length. A similar phenomenon occurs below the aneurysm in the iliac arteries, leading to tortuous iliacs. As many as 20% of aortic aneurysms may have so much tortuosity that they are unable to be fitted with an endovascular graft of this kind. Such systems are unable to conform to the curved walls of the vasculature due to the tortuosity caused by the growing aneurysm.
A specific problem is the xe2x80x9cangulationxe2x80x9d or bend in the neck of the aorta, where it meets the upper part of the aneurysm. This angulation may result in several problems which limit the effectiveness of traditional endovascular graft systems which do not have designs that conform to the tortuosity and angulation above the aneurysm. First, since these systems are typically anchored above the aneurysm with a stent, a portion of the stent may extend into the blood flow path, creating turbulence which may result in blood clotting. It is well-known that in coronary vessels, stents used to treat constrictive lesions must be well apposed to the wall of the vessel to prevent the possibility of thrombosis. Second, a non-conforming upper stent will not place the upper end of the graft in good apposition to the aortic wall, making it difficult to obtain a good seal with a conventional endovascular graft system. Such is illustrated in FIG. 2, showing a generic endovascular graft attached to a conventional non-conforming expanded metal stent in the neck of a tortuous aortic neck. Since this conventional stent will not conform to the tortuosity of the aorta, an upper edge 1 of the stent extends into the blood flow path increasing the chance of thrombosis. Further, a lower edge 2 is not apposed to the wall of the aorta so that the graft material 3 affixed to it does not properly seal. A third problem with non-conforming attachment systems is that once placed in tortuous or angulated aneurysmal anatomy, they are unstable and can xe2x80x9cpop-outxe2x80x9d of position. The attachment system shown in FIG. 2 is an example of an unstable attachment system. Conventional endovascular graft systems having an attachment system intended to project across and above the renal artery ostia also pose a different problem since the attachment system obstructs the renal arteries making it difficult, if not impossible, to effect a repair on a renal artery once the stent is in place.
Thus, a need exists for a prosthetic endovascular graft system which will permit stable conformance to bends within an aneurysm, while providing a good seal to the vasculature.
This invention is an endovascular graft system comprising an attachment member which conforms to the contours of the vessel adjacent an aneurysm, permitting a good seal and robust anchoring of the graft with the vasculature. The attachment member is a stent-like structure which will be referred to herein either as an attachment member, an aortic attachment member or a stent.
In one aspect, this invention is an aortic attachment member capable of expanding from a first delivery configuration to a second deployed configuration for placement in a vessel of a patient""s vascular system, the attachment member comprising a cranial zone having a first radial strength, a caudal zone having a second radial strength, and an intermediate zone comprising multiple longitudinal struts located between the cranial and caudal zones, the intermediate zone having a third radial strength. The cranial and caudal zones are separated by and joined by the longitudinal struts. The third radial strength can be lower than the first or second radial strengths. The cross-sectional area of the longitudinal struts is preferably smaller than the cross-sectional area of the material making up the caudal or cranial zones. Preferably, the cross-sectional area is reduced by reducing both the strut width and thickness. Preferably, the caudal and cranial zones have struts patterned in a Z-shape. Alternatively, the cranial zone may have struts shaped in a diamond configuration. The radial strength of the caudal and cranial zones may be approximately equal. In a preferred embodiment, the caudal zone further comprises barbs to assist in anchoring the attachment member. The cranial zone may also comprise barbs to further assist in anchoring the attachment member.
In another aspect, this invention is an endovascular graft system capable of expanding from a first delivery configuration to a second deployed configuration for placement in a vessel of a patient""s vascular system. The endovascular graft system comprises an aortic attachment member having a cranial zone and a caudal zone, each having a first radial strength, and an intermediate zone having multiple joining longitudinal struts located between and connecting the cranial and caudal zones, the intermediate zone having a second radial strength which is less than the first radial strength, the cranial and caudal zones being formed from a self-expanding material. The system further includes a conduit formed of a graft material affixed to the caudal zone of the attachment member.
In another aspect, this invention is a biluminal endovascular graft system capable of expanding from a first delivery configuration to a second deployed configuration for placement in a vessel of a patient""s vascular system, comprising an aortic attachment member, the aortic attachment member comprising a cranial zone having a first radial strength, a caudal zone having a second radial strength, and an intermediate zone comprising joining longitudinal struts located between the cranial and caudal zones, the intermediate zone having a third radial strength, wherein the cranial and caudal zones are separated by and joined by the longitudinal struts. The system further includes a trunk having first and second branch portions formed of a biocompatible graft material and first and second legs adapted to be deployed in a manner such that they extend from the first and second branches, respectively, the first branch and first leg forming a first conduit and the second branch and second leg forming a second conduit.
In a further aspect, the invention is an attachment member for anchoring a graft system at a desired location in a vessel of a patient""s vascular system. The attachment member comprises a first engaging portion, a second engaging portion, the first and second engaging portions comprising a self-expanding material capable of expanding from a delivery configuration to a deployed configuration and an intermediate portion having multiple longitudinal struts, the first ends of the struts being affixed to the first engaging portion and the second end of the struts being affixed to the second engaging portion, the struts being configured such that the first engaging portion can be deployed to engage the walls of the vessel substantially independently of the deployment of the second engaging portion.
In a still further aspect, the invention is an endovascular graft system capable of being deployed at a desired location within a vessel by a catheter introduced into a patient""s vascular system. The graft system comprises an attachment member having a first engaging portion, an intermediate portion, and a second engaging portion, the intermediate portion having multiple longitudinal struts having first and second ends, the first ends being affixed to the first engaging portion and the second ends being affixed to the second engaging portion, the first and second engaging portions being formed of a self-expanding material capable of expanding from a delivery configuration to a deployed configuration, the struts being configured such that the first engaging portion may be deployed so that it expands to its deployed configuration while the second engaging portion is in the delivery configuration. The graft system further includes a conduit formed of a graft material affixed to one of the engaging portions of the attachment member.
In a further aspect, the invention is a biluminal endovascular graft system capable of being deployed at a desired location within a vessel by one or more catheters introduced into a patient""s vascular system. The graft system comprises an attachment member having a first engaging portion, an intermediate portion and a second engaging portion, the intermediate portion having multiple longitudinal struts having first and second ends, the first ends being affixed to the first engaging portion and the second ends being affixed to the second engaging portion, the first and second engaging portions being formed of a self-expanding material capable of expanding from a delivery configuration to a deployed configuration, the struts being configured such that the first engaging portion may be deployed so that it expands to its deployed configuration while the second engaging portion is in the delivery configuration. The system further comprises a conduit formed of a graft material affixed to one of the engaging portions of the attachment member, a trunk having first and second portions formed of a biocompatible graft material and first and second legs adapted to be deployed in a manner such that they extend from the first and second branches of the trunk. The first branch and first leg forming a first conduit and the second branch and second leg forming a second conduit.
In another aspect, this invention is a method for repairing an aneurysm in an aorta with a graft system having an aortic attachment member as described above attached to a trunk having first and second branches adapted to be mated with first and second legs, thus forming first and second conduits, each conduit comprising a graft component. Each conduit has an iliac attachment element such as a stent at its caudal end to allow the caudal ends of the conduits to be secured within a respective iliac artery. The method comprises advancing the aortic attachment member which is attached to the trunk through an iliac artery by means of a catheter; positioning the aortic attachment member within the neck of the aorta; deploying the first engaging portion of the attachment member so that it seats against the wall of the aorta before the aorta has been substantially occluded by deployment of the second engaging portion; deploying the second engaging portion of the attachment member; advancing the first leg by means of the first catheter through the iliac artery to mate with the first branch of the trunk, thus forming a first conduit; advancing the second leg by means of a second catheter through a second iliac artery to mate with the second branch of the trunk, thus forming a second conduit; and deploying the iliac attachment element of the first and second conduits within the iliac arteries.
In another aspect, the invention is a method for deploying an aortic attachment member in an aorta, the aortic attachment member having first and second engaging portions separated by an intermediate portion, the first and second engaging portions being made of a self-expanding material capable of expanding from a first delivery configuration to a deployed configuration. The method comprises advancing the aortic attachment member and attached trunk through an iliac artery into the aorta by means of a first catheter; positioning the aortic attachment member within the aorta a desired location; deploying the first engaging portion of the attachment member so that it seats against the wall of the aorta before the aorta has been substantially occluded by deployment of the second engaging portion; and deploying the second engaging portion of the attachment member.